A Simple High Power, Fast Response Streaming Potential/Current-Based Electric Nanogenerator Using a Layer of Al₂O₃...

Harvesting energy from ambient moisture and natural water sources is currently of great interest due to the need for standalone self-powered nano/micro-systems. In this work, we report on the development of a cost-effective nanogenerator based on a carbon paper-Al₂O₃ nanoparticle layer-carbon paper (CAC) sandwich structure, where the 3D Al₂O₃ layer is deposited via vacuum filtration. This type of device can produce an open-circuit voltage (U_OC) of up to 4 V and a short-circuit current (I_SC) of ∼18 μA with only an 8 μL water droplet applied. To our knowledge, this is the highest voltage yet reported from a single moisture/water-induced electricity nanogenerator using solid oxides and carbon-based materials. A remarkable output power of 14.8 μW can be reached with an optimized resistive load. An LED with a working voltage of 3-3.2 V can operate for a short time with the power from a single CAC device exposed to one 8 μL water droplet. Furthermore, a CAC generator adsorbing as little as 2 μL water droplets every 3 min can also give a U_OC of 3.63 V. We show that CAC devices provide a robust electrical output over more than 200 wet-dry cycles without any deterioration in performance. These units demonstrate much promise as cost-effective electricity generators for harvesting energy from natural sources like rainwater, tap water, snow runoff, and dew. The response time of CAC devices can be as fast as 10-100 ms, making them ideal for applications as self-powered water detectors. The generation of power in this device arises from the streaming current. To assist in the optimization of these devices, we have analyzed how their response is related to such factors as layer thickness, time interval between application of water droplets, and the volume of each water droplet.